This invention relates to expansion valves for refrigeration systems, and in particular, to an electrically operated expansion valve. While the invention is described in particular detail with respect to expansion valve applications, those skilled in the art will appreciate the wider scope of the invention described hereinafter.
Refrigeration systems generally include an evaporator, a compressor, and a condenser. Refrigerant vapors drawn from the evaporator by the compressor are forced into the condenser, where the vapor liquifies. The liquid refrigerant then is returned to the evaporator through an expansion valve. The expansion valve converts the refrigerant from a high pressure liquid to a low pressure gas by passing the refrigerant through a restriction in the valve. Control of refrigerant input to the evaporator can be maintained by inserting a valve member in the restriction of the expansion valve, and adjusting the valve member position in response to a particular external condition.
The majority of prior art expansion valves have been thermostatic responsive devices. Commonly, these prior art devices utilize a diaphragm responsive valve for modulating the refrigerant passing through the restriction. That is to say, the valve includes a valve pin operatively connected to a flexible diaphragm. A spring is biased between the valve and the diaphragm on one side of the diaphragm so as to force the valve pin toward a closed portion of the valve, while the opposite side of the diaphragm is operatively connected to a temperature sensing, pressure generating means. The temperature sensing means conventionally is charged with a gas. The gas expands as temperature increases, thereby raising the pressure on one side of the diaphragm, moving the diaphragm and consequently the valve pin, in a direction so as to open the expansion port or restriction.
Thermostatic controlled expansion valves, while working well for their intended purposes, are relatively complicated in their manufacture in that the temperature sensing means and the valve must be charged and hermetically sealed during valve manufacture.
Electrically controlled expansion valves also are known in the art. In general, an electrically controlled valve should be able to control the refrigeration system more precisely because of its theorically faster response time. More precise control, in turn, should improve the efficiency of the refrigeration system. Presently known electrically controlled valves, however, have not exhibited the faster response times supposedly inherent in this type of valve. That is to say, the refrigerant fluids passing through prior art valve constructions have affected valve operation to such an extent that the response times of the electrically controlled valves are not as good as one would expect, other factors being equal. Consequently, prior art designs often employ a combination diaphragm and electrical actuator system.
The invention disclosed hereinafter overcomes prior art deficiencies by utilizing, in the preferred embodiment, a straight line construction having an electrically operated thermostatic means operatively connected directly to the valve pin of the valve. The thermostatic means includes a plurality of bi-metalic discs alternately placed between and adjacent to a plurality of heater elements. The heater elements include a resistive member which is capable of radiating heat directly to the adjacent bi-metal discs, thereby providing improved heat transfer and quicker response times than other known designs.
One of the objects of this invention is to provide an improved electrically operated expansion valve.
Another object of this invention is to provide an expansion valve having a straight line construction.
Yet another object of this invention is to provide an electrically operated valve having an electrically generated thermostatic means comprising a plurality of bimetallic discs and a plurality of heater elements alternately arranged in the valve structure.
Still another object of this invention is to provide an expansion valve, the operation of which is dependent solely on an electrical input.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.